1. Field of the Invention
The invention relates in general to a pixel structure and a liquid crystal display (LCD) panel and an LCD device using the same, and more particularly to a pixel structure and an LCD panel and LCD device using the same capable of reducing color shift.
2. Description of the Related Art
A conventional multi-domain vertical alignment (MVA) liquid crystal display (LCD) device displays a frame. Color shift may occur and make the viewer feel the colors of an image different when the image is viewed from different view angles. The reason causing color shift is that the liquid crystal has a fixed tilting angle. The transmittance of the light differs at various view angles (a contained angle with the normal line of the panel), changing the mixing proportion of the light passing through the color filter.
To reduce color shift, a single pixel structure is divided into two independent pixel electrodes which are coupled to different voltages. FIG. 1 is a diagram of a conventional pixel structure. A pixel structure 10 is surrounded by two data lines 1 and two scan lines 2. A storage capacitor 3 is divided into a pixel electrode 4a and a pixel electrode 4b, which are coupled to a higher voltage and a lower voltage, respectively. The voltage differential between the pixel electrodes 4a and 4b results in liquid crystal molecules to tilt with different angles. The light emission rates of the liquid crystal molecules at different view angles are approximately the same. Accordingly, color shift is reduced. However, the pixel structures 10 are regally distributed in a panel. A viewer may see dark and bright grids when voltage differential results in different light emission rates.
Therefore, a chevron pixel structure is provided. FIG. 2 is a diagram of a conventional chevron pixel structure. A pixel structure 20 includes a pixel electrode 11 coupled to a low voltage and a pixel electrode 12 coupled to a higher voltage. The electrode 11 and the pixel electrode 12 are separated by a slit 13. A storage capacitor 14 disposed at the central part of the pixel structure 20 is coupled to the pixel electrodes 11 and 12 via the contacts 14a and 14b for stabilizing the voltages of the pixel electrodes 11 and 12, respectively. Protrusions 15a and 15b disposed over the substrate wind through the central part of the pixel electrode 11 and the pixel electrode 12, respectively. As the pixel electrode 11 and the pixel electrode 12 are not regularly disposed as the pixel electrodes 4a and 4b shown in FIG. 1. An LCD panel with the pixel structure 20 provides uniform brightness to a viewer. In order to enhance contrast, the area of the pixel electrode 11 providing a low voltage is larger than that of the pixel electrode 12 providing a high voltage and a ratio is approximately 2:1.
The pixel structure 20 and protrusions 15a and 15b are separately depicted in FIGS. 7A and 7B. Specifically, FIG. 7A is a schematic diagram of the pixel electrodes 11 and 12 over a second substrate of the pixel structure depicted in FIG. 2, and FIG. 7B is a schematic diagram of the protrusions over a first substrate of the pixel structure depicted in FIG. 2.
However, the slit 13 and the protrusions 15a and 15b of the pixel structure 20 at bright mode will affect the aperture ratio and reduce brightness. Furthermore, the protrusions 15a and 15b at dark mode may tilt down the liquid crystal molecules and result in light leakage, further affecting image contrast.